The present invention relates to thermal insulation products, and more particularly to piping, vessels and the like fluid conduits or containers thermal insulation envelops.
These products, usually in the form of sleeves or slabs, are customarily made of foamed polymeric material, mostly polyurethane (hereinafter "PU") in elastic or in rigid forms.
Due to the inherent, open cell structure of PU, it is regarded as less efficient than other, closed cells or pores polymers (e.g. foamed rubber, commercially known under the tradenames "ARMOFLEX" and "VIDOFLEX"), since the closed cells structure avoids convection heat dissipation by the flow of air between and through the open cells.
On the other hand, the closed pores polymers are inferior in other respects: low temperature resistivity and loosing of elasticity upon heating up to elevated temperatures (bendable only up to about 90.degree. C.)--whereas these restrictions do not apply to PU products.
It is therefore the general object of the invention to improve the thermal insulation properties of PU and similar open-cells polymers.
It is a further object of the invention to apply a process for treating PU products so that flow of gas between the cells will be considerably restricted.
It is a still further object of the invention to provide a process through which suitably sized particles are deployed along walls of the passages between adjacent cells, thus impeding the undesirable flow of air.